Manufacture of viscose silk



PATENT OFFICE.

EMILE BRONNERT, 0F M'ULHAUSEN, ALSACE-LORRAINE, FRANCE.

MANUFACTURE OF VISCOSE SILK.

No Drawing.

T 0 all whom. it may concern:

1 3e it known that I, EMILE BRONNERT, a

citizen of the Republic of France, residing at 1 Quai du-Barrage,Miilhausen, Alsace- Lorraine, France, have invented certain new anduseful Improvements in the Manufacture of Viscose Silk, of which thefollowing 18 a specification; It is known that raw viscose can be spun ndiluted sulfuric acid to lustrous threads, 1f measures be taken toinsure the reaction proceeding properly.

- lVhile younger viscose may only be spun with caution in weaker acid,older viscose must be spun in stronger acid which is also warm.

Now it has been found that in order to obtain a thread of extremefineness, the acid concentration and with it the precipitating power ofthe bath must be all the stronger the thinner the individual thread tobe obtained is desired to be. With a bath of pure diluted sulfuric acidor sulfuric acid with for instance as much sulfate of sodium as isultimately present in'the bath when spinning as a condition ofequilibrium or also with salts of other bases and acids, the individualthread strengths of titrations which can be obtained with determinedsulfuric acid baths, act in relation to each other in a mannerapproximately inverse to the squares of the sulfuric acid.concentrations of the baths. On spinning very fine threads according tothe usual method of operation it is, therefore, essential to use arelatively high sulfuric acid concentration of the bath. With so strongan acidity of a bath containing a small percentage of salts, it is,however, with the normal viscose of about 8% cellulose and 7% causticsoda content only possible to spin a relatively well ripened viscoseiftechnically useful lustrous products are to be obtained.

With the many dangers of practical spinning it is, however, desirablethat the composition of the precipitating bath be as independent aspossible of the ripeness of the viscose. So far assistance in thisconnection has mostly been obtained in that, larger uantities of saltswere added to the bath. la'ow it has been found that the proportion ofthe degree of ripeness of the viscose to the acid concentration can bechanged in a far reaching manner without prejudice to the luster andfullness of the product, if

Specification of Letters Patent.

Patented May 3, 1921.

Application filed September 10, 1920. Serial No. 409,441.

spinning of cellulose hydrate threads, which are insoluble in water,from the usual spinnlng openings of 0.1 mm. diameter. However, with suchsolutions, attention must be given not only to the sulfuric acidconcentration at the time of precipitating the threads, but also to aregular feed of spinning solution corresponding to the simultaneousnumber and the titer of the threads desired at the time to form acollective thread and also to the speed of drawing off, both of whichlatter factors determine the consumption of spinning solution. I

It is preferable to increase the quantity of litctic acid, the youngerthe viscose to be use To appreciate the peculiar effect of the newprocess a comparison of Examples I and V with the other examples may behad.v

Example I.

In a warm bath of 45 with 135 gr. sulfuric acid per liter, there isintroduced through nozzles of about 0.10 mm. diameter, the usual rawviscose of about 8%, relatively young, of say about 9 ripeness (chloridof ammonium standard). The threads of about 7 deniers rising from thebath with a speed of about 45 m. are at once washed and then treatedfurther in the usual manner.

The finished product does not present anything worthy of remark.

The threads have a more or less round elliptic cross section.

E wample I l Eam te III.

A sulfuric acid bath of 135 gr. sulfuric acid per liter, but otherwisesimilar to that employed in Example I, is mixed with 50 gr. lactic acidper liter and the same raw viscose of 9 ripeness (chlorid of ammoniumstandard) is again introduced into the bath. The spinning process actionis almost perfect. The final product shows in cross section formssimilar to those obtained by Example II, only the toothing or dentationsomewhat less and coarser, the softness and luster of the product are onthe other hand quite prominent so that it equals the best products fromacid baths which contain much salt, in fact is even superior to them.The elasticity of the threads increases with the increasing lactic acidcontent of the bath.

Whether the lactic acid is able to force back the free ions of thesulfuric acid similar to the salts forming bisulfates need not bediscussed. The effect is at all events a most peculiar one.

This is brought out in a marked manner by a comparison of the resultsillustrated in Examples IV and V.

E wam-plc IV.

Young viscose, this time of 12 ripeness, with a spinning length of 20cm. is spun as stated in the other examples into a 45 warm spinning bathof 135 gr. sulfuric acid and 50 gr. lactic acid per liter. There isagain produced with great certainty a directly washable thread whichafter finishing, is of very fine luster and of remarkable softness, bodyand elasticity.

Example V (to illustrate prior art.)

If on the contrary the same young viscose of 12 ripeness isspun in thesame manner in warm sulfuric acid of 135 gr. per liter without theaddition of lactic acid, then only a much duller and much thinner threadthan those produced bythe processes described in Examples II to IV, isobtained evenif the bath has been enriched up to the same equilibrium ofabout to gr. sodium sulfate per liter.

The lactic acid is therefore to a pronounced extent quantitativelydifferent from the action of the sulfate; the presence of sulfates andother salts, however,-is not disturbing. It does not itself appear tohave any actual precipitant action as a'thread former, it requires thecooperation of salts or acids.

If, as already proposed a spinning bath be used of a sodium lactatesolution with an addition of about gr. lactic acid per liter, then onlya water soluble thread is obtained which must be subs quently fixed bymineral acid or the like.

If as much of the uni-basic lactic acid per liter of water be taken aswould be equivalent to the acidity of 100 gr. sulfuric acid that is tosay about 200 gr. water free lactic acid per liter, then no threadformation takes place when a raw viscose solution of 9 ripeness ispressed in.

Also when viscose of 9 ripeness is allowed to flow into a heatedspinning bath of about gr. anhydrous lactic acid and 90 gr. sulfuricacid per liter, then threads of 7.5 deniers can hardly be spun.

Viscose can only be spun to directly washable threads when the sulfuricacid content of the spinning bath is increased to 115 gr. per liter. Itis therefore demonstrated that the lactioacid is substantially withoutinfluence upon the thread formation, as the viscose in question can alsobe spun just as smoothly although not of the same quality in sulfuricacid alone of ll gr. per liter.

These sulfuric acid and oXy-acid baths, and especially such with lacticacid, are preeminently and quite suitable for the production of fine andultra-fine threads, of course as well for instance for threads ofordinary caliber.

The described draw-spinning process is particularly suitable and yieldsa very fine fluff free product.

The friction of the threads on the spin- I ning bath particles isapparentlyreduced to a minimum. The sodium sulfate, which reaches acondition of equilibrium, has no harmful effect at all, and does notcrystallize upon the threads, as this is in any case prevented by thesimultaneous formation of deliquescent sodium lactate.

I claim:

1. A spinning bath for use in the manufacture of viscose silk,containing sulfuric acid and lactic acid.

2. A spinning bath for use in the manufacture of viscose silk,containing sulfuric acid and lactic acid, the quantity of lactic acidbeing proportioned substantially inversely-to the age of the viscose tobe treated.

3. A spinning bath for use in the manufacture of viscose silk,containing sulfuric to the fineness of the thread to be produced.

In witness whereof, I have hereunto signed my name in the presence oftwo subscribing witnesses.

EMILE BRONNERT.

Witnesses L. R. Santa, N. ScHLUMBoRcnR.

